About half the height of standard-profile nuts, these fit in spaces with low clearance. You can also use them as jam nuts by threading them against another hex nut to hold it in place.

Versatile yet economical, these are the most commonly used locknuts. The nylon insert grips the screw to prevent loosening from moderate vibration without damaging threads. However, the insert may become brittle if exposed to high temperatures. These locknuts are reusable a handful of times, but the holding power decreases with each use.

Irregularly shaped threads at the top of these locknuts grip the screw for a stronger hold than nylon-insert locknuts. Although the threads prevent the nut from backing out due to vibration, they also increase the effort to install and remove. To get these nuts off, you may need special tools, such as an impact wrench or propane torch. Nuts are not reusable.

Also known as reversible locknuts, these thread on from either side, so you don't have to worry about fastening them incorrectly and damaging your screw. The irregularly shaped threads in the middle grip the screw for a stronger hold than nylon-insert locknuts. Although the threads prevent the nut from backing out due to vibration, they also increase the effort to install and remove. To get these nuts off, you may need special tools, such as an impact wrench or propane torch. Nuts are not reusable.

The star-shaped head has more points of contact than a hex head nut, so you can achieve a better grip and a tighter fit without flattening the sides of the nut. Great for cramped spaces without a lot of clearance, these nuts twist on from any angle with a standard wrench. They have a flange that distributes pressure evenly across the mounting surface without the need for a separate washer. Also known as collar nuts.